Mobile networks may increase available bandwidth, throughput or capacity using techniques such as carrier aggregation (CA), in which multiple frequency bands may be supported simultaneously. As an example, a mobile device may communicate on multiple frequency bands with a single base station. As another example, the mobile device may communicate to multiple base stations on different frequency bands. Some associated tasks, such as security and allocation of communication bearers, may be challenging for CA arrangements, especially those in which multiple base stations are used. Accordingly, there is a general need for methods that enable CA operation, and particularly CA operation with multiple base stations.